[PATCH 4.19 33/50] net: bridge: mcast: fix stale ipv6 hdr pointer when handling v6 query

[Greg Kroah-Hartman]

From: Nikolay Aleksandrov <niko...@cumulusnetworks.com>

[ Upstream commit 3b26a5d03d35d8f732d75951218983c0f7f68dff ]

We get a pointer to the ipv6 hdr in br_ip6_multicast_query but we may
call pskb_may_pull afterwards and end up using a stale pointer.
So use the header directly, it's just 1 place where it's needed.

Fixes: 08b202b67264 ("bridge br_multicast: IPv6 MLD support.")
Signed-off-by: Nikolay Aleksandrov <niko...@cumulusnetworks.com>
Tested-by: Martin Weinelt <mar...@linuxlounge.net>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/bridge/br_multicast.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1510,7 +1510,6 @@ static int br_ip6_multicast_query(struct
                                  struct sk_buff *skb,
                                  u16 vid)
 {
-       const struct ipv6hdr *ip6h = ipv6_hdr(skb);
        struct mld_msg *mld;
        struct net_bridge_mdb_entry *mp;
        struct mld2_query *mld2q;
@@ -1554,7 +1553,7 @@ static int br_ip6_multicast_query(struct
 
        if (is_general_query) {
                saddr.proto = htons(ETH_P_IPV6);
-               saddr.u.ip6 = ip6h->saddr;
+               saddr.u.ip6 = ipv6_hdr(skb)->saddr;
 
                br_multicast_query_received(br, port, &br->ip6_other_query,
                                            &saddr, max_delay);